Electrical transposition system



March 24, v1925. 1,530,537 H. A. AFFEL ELECTRICAL TRANSPOSITION SYSTEM Filed Aug. 31, 1922 lil/ze /l 2 like www WM A TTORN E Y Patented Mar. 24, 1925.

UNITED STATES PATENT OFFICE.

HERMAN A. AFFEL, 0E BROOKLYN, NEW YORK, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGBAPH COMPANY, A, CORPORATION OF NEW YORK.

ELECTRICAL TRANSPOSITION SYSTEM.

Application .mea August 31, 1922. serial No. 585,436.

To all whom t may concern:

Be it known that I, HERMAN A. AFFEL, residing at Brooklyn, in the county of Kings and State of New York, have invented'cer- 'tain Improvements in Electrical Transposition Systems, of which the following is a specification.

This invention relates to electrical transposition systems and particularly to an arrangement for transposing a line circuit adapted for the simultaneous transmission of a-plurality of frequencies or bands of frequencies.

Heretofore in the operation of systems in which signaling was carried on by means of a relatively low frequency current or range of low frequency currents such as required for voice transmission, where .it has been necessary to transpose pairs of wires. to prevent mutual interactions, due to inductive or capacity effects between them, it has been customary to introduce' the transpositions at intervals which were short relative to the wave lengths of the .electric currents concerned. This has usually entailed no particular hardship, since, as noted above, the frequencies were relatively low and the wave lengths correspondingly long.

When transposing wires to prevent mu` tual interactions, or in other words crosstalk, between paralleling pairs at the higher frequencies for the operation 'of high frequency` telephone or telegraph systems, i. e., carrier current systems, the problem becomes increasingly diflicult. rIhe wave lengths involved in this case are relatively short and in order to carry out the general principle of providing transportation intervals which are a small fraction of the wave length, requires, in many cases, the' insertion of transpositions at points extraordinarily near to# gether. In fact the number of transpositions required and the physical `difficulty involved in obtainin the accurate fre uency spacing, often ren ers it impractica le to. employ such an arrangement, effective throughout a wide range of frequencies. A les r number of transpositions may,.howA ever, be provided Where it is desired to have the action effective only at a' single frequency over a relatively narrow range of frequencies because in this case the rapid phase changes act in a sense to transpose the cu'rents automatically at frequent interva s.

It is the object of this invention to provide means whereby line circuits may be effectively transposed to prevent interactions between circuits throughout' a wide range yof frequencies, covering low frequencies as well as high frequencies, witha minimum number of. transposition points. The particular .feature by which this objective is achieved is the use of what may be termedl selective transpositions, namely, means whereby a line circuit may be eEectively transposed -at a given point for a particular frequency, or band of frequencies, and at the same time rendered untransposed at the same point for other bands of frequencies vthan those for which it is desired to trans- 1,s3o,537 y a selective transposition as above noted, the

points at which both circuits-are required lto be transposed being served by a simple transposing ofthe wires in the ordinary manner. y

, Other objects of this invention will be ap. parent from the following description when readin connection with the attached drawing, in whiclrFigure 1 showsa simple form of embodiment of the invention, Fig. 2

lshows the application to a line circuit of a plurality of units such as are shown in Fig. l, and Fig. 3 shows the application of the invention toa directive radio antenna.

In Fig. l, 1 and 2 represent two sections of a line which is adapted to have transmitted thereover a plurality of frequencies, or bands of fre uencies. Inserted between the Sections .1 an 2 of the said line circuit, and in series therewith, is an electrical network which may be termed, for the purpose of description, a transposition group.

It is the purpose of this circuit to divide the frequencies being transmitted over the line into different bands, thereby permitting the circuit carrying one or more of the bands to be crossed, or transposed, while maintainloo shown in Fig. 1, it is to be understood that n the invent-ion is not limited to this particular number, but may be varied without changing the scope of the invention.' The filter designated A is of the type known in the art as a bandssuppression filter and is f disclosed in the patent to G. A. C-ampbell,

No. 1,493,600, darf-,ed May is, 1924. This filter, the transmission frequency characte-ristie of which is represented by the dotted curve a in Fig. l, is adapted to suppress a particular band of frequencies such, forexample, asl that represented by fl-fz and to transmit readily, or substantially' so, all Jfrequencies lying without that band. This is clear from a consideration of Fig. 1, which shows the varia-tion of loss of the net` work A for various frequencies impressed upon the said network. Thus, it-will be I seenthat for frequencies below f1 and above f2, the transmission loss is fairly low, whereas it is v'ery high for the band lying between f1 and f2. The filter B, whose characteristiceurve is designated b in Fig. 1, is of the type known as ba'ndass filters. This filter, with the exception o the transposition of the conductors designated 3, is f disclosed in the patent to G. A. Campbell, 1,227,113, dated May 22, 1917. A consideration of the characteristic curve, shown in Fig. 1a shows that the transmission loss to current-s below f1 and above f2 is very great, whereas the transmission loss lying between these limiting frequencies is relatively small. This means. of course, that the band )c1-f2 will be readily transmitted through a filter of the type represented by B,but that frequencies or bands of frequencies lying without those limits will be substantially suppressed. Since filter A suppresses the same band of frequencies which is readily transmitted by filter B, these filters are termed complementary and are hereinafterreferred to by that term. By reversing the conductors of the filter B at the point 3, the line is electrically transposed with respect to the currents that are transmitted through the filter B, but the line is not transposed with respect to currents of the frequencies transmitted through the filter A. It will be clear, therefore, .that if, for example, a band of frequencies f,-f2 and'auother band of ,frequencies lying without the range of the said first band, arrive vover the section 1 of the line circuit, the

band )i1-f2 will be transmitted through the filter B and, due to the transposition 3, will be impressed in an o posite sense across the section 2 of the said me circuit. The other frequencies will not pass through the, filter B, but will be transmitted through the filter y A, and since the conductors tliereofare not reversed, the said other band of frequencies will be impressed across the section 2 of the line in the same sense in which they were impressed across the line 1.

The application of a plurality of transposition groups, such as shown in Fig. 1, is illustrated'in Fig. 2. In this figure, 1, 2, 3, 4 and 5 represent five sections of a line circuit which are connected together by means of a plurality of transposition groups, the

object of which is to transpose the said line for a particular frequency, or band of frequencies in order to prevent cross talk into some adjacent pair of wires. sumed that the points X and X1 represent points at which it is desired to transpose to prevent cross talk forfrequencies lying within the band )c1-f2 and Y and Y1 represent desired transposition points for preventing cross talk for frequencies lying within the band )ts-fp There should accordingly be inserted at X and X1 a transposition group comprising a filter B adapted to transmit the band of frequencies fl---f2 and to suppress all other frequencies, and a filter A which will transmitl all of the said other' frequencies and will suppress the band f1-f2. The transposition grou shown at Y and Y1 comprises a filter 15),' which is adapted to transmit the band of frequencies 3-f4 (viz, the said other frequencies transmitt-ted by the filter A at points X and X1) but to suppress the baud fl-fz, and a filter i, which is adapted to transmit the band f,--f. but to suppress the band )Q -f4. Each of the filters B and D has its conductors reversed as representedby 3 in Fig. 1. Aecordingly, itwill be seen that if two bands of frequencies, for example, )c1-f;I and fp f, arrive over the ,section 1 of the said line, the band )i1-f2 will be transmitted through the filter B and will be impressed across the line 2 in an opposite sense. The band f3- 4 will be transmitted through the filter A and impressed across the section 2 in the same sense in which it was impressed across the section 1. These two bands will then be impressed across the tranposition group at Y. The band fa-mf,t will be transmitted through the filter D and, due to the transposition therein,

t-he band will be impressed across the section Let it be as- 3 in an opposite sense to that in which it section 2. Accordingly, it will be seen that the line, whichis made up of a. plurality of sections designated, for example, l to 5 inelusive, is transposed at the points X and X, for currents of the band )f1-f2, but is not transposed for all other frequencies. At points Y and Y, the said line is transposed for currents of the frequencies fa- 4 but' is not transposed for, currents of ot er frequencies. l

It will be apparent that any number of transposition groups may be used in a line such as shown in Fig. 2, depending upon the number of bands of frequencies for which it' is desired to transpose the said line.

The arrangement shown in Fig. 3 represents the application of this invention to a directive loopantenna, the obect of which is to make the antenna better responsive to waves received from a particular direction. In my copending application,h Serial No.

607,193, filed Dec, 15, 1922, I showed the use of a transposed loop antenna., which, by the proper locating of the transposition points, was better adapted to receive waves ofa particular frequency, or band of frequencies,

, v and to exclude or suppress currents of otherv frequencies. Such an arrangement, as was therein disclosed, tended to minimize the effects of static and also of interference from stations other than that from which it was desired to receive signals. The 'arrangement shown in Fig. 3 is an application of the present invention to the antenna broadly shown and claimed in the said oopending application. In Fig. the antenna per se is represented by a plurality -of sections designated 10 to 15 inclusive. Across the one end of section 10 is a terminating resistance 16, which simulates the characteristic impedance of the antenna. The other end of section 10 is connected with the filters A and B, the filter B being designed to transmit.. for example, the band fl-f'g and filter A being designed to suppress that frequency but to transmit all other frequencies. By the proper location of the transposition groups at the points X1, X2 land X3 the antenna is made highly selective for frequencies lying within the desired band and is made nonselective for other frequencies. While I have shown two uses to which my invention may be applied, its scope is vnot limited, since many other and varied uses will occur to those familiar with the art. Furthermore, while I have shown the use of Yband filters of various types in the drawing in which the invention is embodied, and have described these particular'types of filters in the specification, it must be understood'that the invention is not limited to these particular types of filters. Nor is it limited to the transmission of bands of frequencies since the invention is applicable to the trans- -position of a transmission circuitfor a. plu- `tary in frequency selection whereby fre- 8O quencies transmitted by one filter will be suppressed by the other, and one of said filters having a transposition therein whereby the transmission circuit will be transposed at that point for the frequencies transmitted by that filter.

2. In an electrical transmission system, the combination with a line adapted to transmit a plurality of hands of frequencies, of a group of filters inserted between sections ofthe said line, the Said filters being connected in parallel and of the complementary band-pass and baud-suppression types, the band-pass filter having its conductors transposed whereby the said line will be transposed for the band of frequencies transmitted through the said band-pass filter.

3. In an electrical transmission system, `the combination with a line adapted to transmit a plurality of bands'of frequencies, of 100 a group of filters inserted between sections of the said line, the said filters being con-v nected in parallel and of the complementary band-pass and band-suppression types, so designed that the band of frequencies 1o.', transmittable through one will be suppressed by the others, the band-pass filter having its conductors transposed whereby thesaid line will be transposed for the band of' frefplenpiiles transmitted through the said band-pass 11o ter.

4. In an electrical transmission system. the combination -with a line circuit adapted to transmit a plurality of frequencies, of a plurality of filters, one of said filters being adapted to transmit readily one of the said frequencies and to suppress the other frequencies, and the other of said filters being adapted to transmit readily the said other frequencies and to suppress the frequency transmitted by the first 'mentionedv filter, the said first mentioned filter having its circuit transposed so as to effect a transposition of the line circuit for the frequency transmitted therethrough.

5. In an electrical transmission system, the combination with a line adapted to transmit a plurality of frequencies, of a group of filters arranged in parallel with each other, the said group being inserted between .sections of the said line, one of said filters being ada ted to transmit readily one of the said requencies and4 to suppressA the other frequencies, and the other of' said filters being adapted to transmit said other frequencies and to suppress the said first mentioned frequencies, the said line being transposed through the said first mentioned` f filter. A

65 In an electrical transmission system, the' combination with a line adapted to transmit a plurality of bands of. frequencies, of a plurality of groups of parallel filters connected in series with the said line, the filters of eachgroup being of the complementary band-pass and band-suppression types, the band-pass filter having its conductors transposed whereby the line Will be transposed for the band of frequencies transmitted therethrough, and similar groups .being spaced'along said line at intervals representing a transposition section for the particular band of frequencies4 transmitted by the band-pass filter of the group.

7. In an electrical transmission system, the combination with a line adapted to transmit thereover a plurality ofbands of frequencies, of a plurality of groups of filters connected therewith, each group comprising a band-pass and a band-suppression filter of the complementary types, the said bandpass filter of veach group having its conductors transposed, thereby effecting a transpositionof the said line at that point for the band of frequencies passed by thesaid filter, similar groups being spaced along the said line at intervals representing a transposition section for. the band of frequencies passed by the band-pass filter of the said group. Y l

l8. In au electrical transmission system, 'the combination Witlfa line adapted for the transmission of a plurality of bands of frequencies, of a group of parallel filters in series with the said line, the said filters being of the complementary band-pass and of arallel filters also in series with the sai line, the said filters being of the complementary type designed so that the band transmitted by the band-pass filter of the second group will be different from the band transmitted by the similar filter of the said first group, the said band-pass filter of each group having its conductors transposed, thereby effecting a transposition of the line at the said points for the particular bands ,Y

of frequencies transmitted through the respective band-pass filters.

9. In an electrical transmission system, the combination with a line adapted for the transmission of a plurality of bands of frequencies, of a plurality of groups of parallel filters in series With the said line, the s'aid filters of each group being of the complementary band-pass and band-'suppression' types, and corresponding filters of all the groups having similar transmitting, and suppression characteristics, and a plurality of other groups of parallel filters also in series with the said line, the said filters of each group being of the complementary type, and corresponding lters -of the various groups having the same transmitting and suppression characteristics, but so designed that the band transmitted by the band-pass filter of one of the latter groups will be different from the band transmitted by the corresponding filter of one of the former groups,

the said band-pass filters of all groups han`Y` ing their conductors transposed to effect av transposition of the line for the particular band of frequencies transmitted thereby, the groups of each of said plurality of groups being spaced along said line at distances apart representing a transposition section for the particular band of frequencies passed by the hand-pass filters of each group.

In testimony whereof, I- have signed my .name to this specification this 29th day of August, 1922.v

HERMAN AFFEL. 

